Dream sprayer

Rhonda J. Brooks | Aug 01, 2000

Last spring, Bill Coppess had his doubts about the new double-nozzle sprayer prototype he was about to try. It looked too simple to deliver on its developer's claim to reduce standard herbicide rates by half while still providing equal or better weed control. But after 1,500 acres and nearly a 50% total reduction in herbicide use, the no-till corn and soybean grower happily acknowledges that the seemingly simple system works.

"It's pretty exciting," says Coppess of Darke County, OH. "The more I used it in my fields, the more confident I got; plus, it saved me quite a bit of money."

Coppess says he went from $40/ acre for post herbicides to about $20/acre this year and adds, "If I'm lucky, I may be able to get costs down below that and still achieve acceptable weed control."

That goal is feasible, according to Robin Taylor, a research scientist at Ohio State University and one of the chief developers of the double-nozzle system. Taylor says each of the six Ohio farmers who used the prototype this year achieved a 50% reduction in herbicide use. Some were even able to secure acceptable weed control with as little as 33% of their typical product use rates.

Simple design. The new double-nozzle system uses two tanks, one to hold water, the second to carry the herbicide. It also requires a set of parallel hydraulic units. One carries a set of flat-fan nozzles used to spray water in large, coarse droplets at about 30 to 40 psi. The second hydraulic unit holds nozzles that spray a pattern of very fine herbicide droplets at a flow rate that equals about one-fourth that of the coarse nozzles.

Mounted on a spray rig, the two parallel rows of nozzles are angled to face each other. When the sprayer is in full operation, the larger water droplets coming from the coarse nozzles intersect and capture the smaller herbicide droplets sprayed by the fine nozzles. Where the water and herbicide meet, roughly 7 to 10 in. out from the nozzles, the spray clouds mix and the water droplets pull the herbicide droplets onto the weeds. As the water droplets hit the plant surface, they shatter, which releases the herbicide droplets and propels them by kinetic energy into the plant canopy where they then go to work.

"The effect of the kinetic energy is kind of like race car drivers who tuck their cars in behind each other to take advantage of the low pressure that's created by the car ahead," Taylor explains. However, he says that same analogy using a bus and a bicycle better demonstrates the difference in size between the water and herbicide droplets. He adds that the two vastly different-sized droplets are critical to the system's design.

To ensure that the herbicide used fully meets and meshes with the water, the fine nozzles are mounted on the hydraulic unit to face in the direction the spray rig is traveling. This practice also helps minimize any potential herbicide drift and the opportunity for evaporation.

For now, the double-nozzle system works only with postemergence products that are broadcast applied. Coppess used the system this year for both burndown and postemergence applications with six or more grass and broadleaf products, both alone and in tankmix combinations. He reports good results across the board on weeds ranging from grasses to Canada thistle, ragweed, lambs-quarters, waterhemp and velvetleaf.

Fall introduction. Ohio State holds the patent on the device and has licensed Spray Redux, based in Cleveland, to manufacture it. The company plans a full-scale introduction of the system during the Ohio State University Farm Science Review this fall.

Sales are projected to be $200 million over the next five years. Spray Redux says its target market is growers with between 400 and 3,000 acres. "That's where the system has its best fit," Taylor says.

Fast payback. In most cases, farmers can retrofit their existing hydraulic sprayers for as little as $2,500 with a top-end cost of $5,500, depending on their specific needs. The base price covers a standard nozzle bracket assembly kit, with a standard unit being about 20 nozzles, plus an extra pump. Taylor says if a grower is unable to use two pumps on his sprayer, he will need to purchase an injector, which will jump the cost to that top end. Either way, the investment pays for itself quickly, Taylor explains.

"A grower with 400 acres typically spends between $3,000 and $6,000 on herbicides each year," he estimates. "With a standard hydraulic sprayer retrofitted with the double-nozzle kit, the grower may invest $2,500 but should only need half as much product that year, so it's possible the system will pay for itself in one year."

Coppess believes the investment is sound for any grower, especially since the sprayer can always be used for conventional applications again if the double-nozzle system doesn't work out for some reason. He adds that it takes only a couple of days' labor to retrofit a sprayer: "It makes for a good wintertime project."

Environmental bonus. Another big plus for the double-nozzle system is that it fits well with farmers' increasing need to exhibit good environmental stewardship, says Roger Bender, extension agent for Shelby County, OH. Bender, along with a small group of concerned farmers, worked last year to submit a grant to the state EPA that will offer area growers an equipment buy-down plan. EPA approved the grant, and now farmers operating in the Upper Great Miami River watershed and the Loramie Creek watershed, which together impact more than 500,000 Ohio acres, can receive a 20% refund when they buy the double-nozzle sprayer kit.

"They turn in their receipts to us, and if they spent $2,500, we refund them $500," Bender says. "It makes the financial risk minimal, and the potential economic and environmental returns significant."

While Bender is a proponent of the system, he does advise growers to approach the use of it, as with any new technology, with caution until it becomes a more proven entity. Because the one set of nozzles sprays a fine droplet pattern, Bender encourages growers to "watch the wind factor."

Coppess agrees. "I haven't seen any drift, but I'm still cautious," he says. "We had one day when we were running about 9 mph across the field into a 3 mph wind, and that concerned me, although I didn't see any drift problems occur."

Bender says the potential advantages from the double-nozzle system prob-ably outweigh any concerns. He states: "This is another movement in agricultural technology that allows farmers to responsibly use herbicides, along with filter strips and other stewardship practices, to achieve good weed control while maintaining good environmental practices."